The biology and management of herring and other pelagic fish stocks in the Firth of Clyde

Abstract

SynopsisThe herring population inhabiting the Firth of Clyde has supported an important fishery for hundreds of years. The basis for this fishery was until recently a stock of spring-spawning herring which spawn on Ballantrae Bank in the period February-April and which was investigated intensively by means of larval surveys from 1958 to 1979, when it had decreased to a very low level. In the late 1960s there was evidence of a change in the composition of the landings and during the 1970s and in the present decade the majority of fish caught have been of autumn-spawned origin. There is no evidence of significant autumn-spawning in the Firth of Clyde and autumn-spawning herring in advanced stages of maturation appear to leave the Clyde, returning by the time the fishery opens the following spring.The spawning origin of autumn-spawned herring in the Clyde has been investigated by tagging experiments, and recaptures have been made in the Irish Sea, off the northwest Irish coast and further north along the west coast of Scotland. However the spawning area of the majority of the fish is unknown.The herring fisheries in the Clyde, originally carried out by ring-net and anchored drift-net but now mainly by pair-trawl, have been managed by closed seasons and in the past few years by total allowable catch regulations under the control of the European Community.There is also a population of sprats in the Firth of Clyde which supports a small fishery and spawning of this species takes place earlier in the Clyde than elsewhere around Scotland. Mackerel also make annual incursions into the Clyde and support a small summer fishery. Factors affecting the abundance of pelagic fish species in the Clyde are discussed.